The discussion of the modes of selection brings up the contrasting concepts of competition and cooperation. Nature positions species both as partners in survival and as rivals. On the one hand, the battle to survive involves competition for limited natural resources, as only certain organisms with advantageous variations are able to survive over others in their particular environments. On the other hand, the interaction between species during the competition also leads to cooperation. For example, the case of a planted tree allowing other plants to flourish around it suggests a mutually beneficial relationship between the tree and plants that ensures their collective survival.
The concept of the struggle for existence may be applied, by extension, to human society. If geometrical population increase is limited in the natural world due to geography and natural resources, human population increase must also have its limits. Do humans engage in a competition for continued existence? If so, do they have to fight one another to survive? Or, might humans work together to survive, as in Darwin’s example of the tree and plants? Also, are humans with the most advantageous positions (in the workforce, for example) winning the battle? In a broader sense, the implied question of whether humans fight to live again casts doubt on the strictness of the separation between humans and the natural world. What Darwin’s work says about human life spawned much of the controversy surrounding The Origin of Species—and modern evolutionary theory.